The present applicant has disclosed in the Patent Laying-Open Gazette No. 9-323495 a free-inking applicator (viz., a writing tool) improved such that ink can smoothly be supplied enabling a continuous writing. This applicator for a writing use comprises a cylindrical ink reservoir and a fiber bundle tip, wherein the ink effluent from the reservoir flows through said tip due to capillary action. The applicator further comprises a valve assembly disposed in a distal region of the ink reservoir. Characteristically, this valve assembly is composed of a spherical valve body and a valve chamber that has a valve seat for supporting the valve body normally resting thereon. The valve seat has a forward opening and the valve body is movable fore and aft within the valve chamber. A spring urges the valve body towards the seat so that the tip disposed ahead the valve assembly has its rear end kept in contact with a forward portion of the valve body.
In the prior art applicator of the described structure, the spring disposed in the valve chamber forces the valve body to stop the forward opening lest any amount of ink should flow out of the applicator not being used. If however the tip is pressed against a paper sheet or the like to apply the ink thereto, then such a pressure to the tip will automatically push the valve body rearwards. As a result, the tip will be soaked with the ink continuously and at a moderate flow rate. Thus, the ink is prevented from trickling down in drops from the tip, but never causing the user to discontinue his or her writing motion for intermittent feed of the ink to the applying tip. There is no fear of any excessive amount of ink that will disable smooth and fine writings.
FIGS. 2 to 5 in the Gazette 9-323495 show the prior art examples wherein the applying tip has its proximal end of a diameter larger than that of the forward opening of the valve chamber. The valve body has a distal portion protruding forwards through the opening so as to contact the proximal end of the tip. The ink effluent through this opening is thus surely absorbed by and into this applying tip, thereby avoiding any dripping of the ink off said tip.
On the other hand, some of the known applicators comprise each an ink reservoir whose proximal or rear end is opened. A back-flow inhibitor such as a polybutene gel inserted in the rear region of the reservoir is capable of sliding therein in an axial direction. This inhibitor stopping the back-flow of ink does prevent ambient air from entering the reservoir's deep region in which the ink is retained. As the amount of the ink held in said reservoir decreases, the inhibitor will gradually move forwards ensuring smooth feed of ink.
In such a prior art structure, it may be necessary to suppress the flow rate of ink. For this purpose, the valve body may have to be of a diameter slightly less than the inner diameter of the valve chamber in order to reduce clearance between said body and the inner periphery of said chamber. In spite of those diameters nearly equal to each other, the valve body must surely seal the valve seat with the forward portion of said body sufficiently protruding from the forward opening out of the valve chamber when the applicator is not in use. To meet this requirement, it may be necessary for the valve seat to be of a concave shape precisely commensurate with the outer periphery of the valve body. However, such a machining of a material for the valve chamber is extremely difficult.
The valve body may, for convenience' sake, be a so small ball that the ordinary caulking process is feasible to form such a valve seat as providing a sufficient forward protrusion of the valve body and a reliable sealing effect thereof. An enlarged clearance around this body will raise the ink flow rate to an undesirable extent to cause the ink dripping. If viscosity of the ink and back-flow inhibitor is considerably low, then this drawback will become severer.
Therefore, a primary object of the present invention is to provide an applicator as well as an ink- or liquid-feeding mechanism incorporated therein, wherein its valve assembly is easy to manufacture and assemble, with the ink or liquid being capable of application to a foreign article at a moderately suppressed flow rate.
As discussed hereinbefore, the prior art writing tool is constructed such that a writing pressure causes a valve body to be retracted a little distance to open the valve assembly to thereby provide a small clearance through which an ink is dispensed. For ensuring a smooth flow-out of the ink, it is of a viscosity of about 100 mPa·s (viz., centipoise) or less. In order to prevent a superfluous discharge of the ink having such a low viscosity of 100 mPa·s or less, a highly viscous follower is disposed in the reservoir behind and in contact with a column of the ink. The follower will exert a viscosity resistance for the ink column so that the ink flows out through the opened valve at an appropriate rate.
Usually, the prior art followers are blocks of a polybutene gel. The present inventors have confirmed through their experiments that the polybutene gel would drastically change its viscosity in response to ambient temperature. In an atmosphere of a temperature of 5° C. corresponding to the winter room temperature, the polybutene gel will show a viscosity of about 100,000 mPa·s. In another atmosphere of a temperature of 35° C. corresponding to the summer room temperature, that gel will show a considerably lowered viscosity of about 35,000 mPa·s or less. If the follower must merely serve as a back-flow inhibitor, then such a polybutene will suffice. However the follower has to serve also as a flow regulator for controlling the flow rate of an ink or the like liquid commencing to flow out in response to small distance displacement of the valve body. Thus, there has been observed a problem that a drastic change in viscosity due to change in temperature would undesirably result in variation of flow rate of the ink or liquid to be applied, to such a degree as causing the ink dripping or scratchy writings.
Therefore, a second object of the present invention is to provide a liquid applicator whose valve body is movable a small distance to open the valve to smoothly flow out the liquid having a viscosity of 100 mPa·s or less at a moderate rate, without being adversely affected by any actual temperature change in living atmospheres. Reliable performance free from any liquid dripping or scratchy application has to be afforded herein.
Further in the described prior art applicators, an idle long elapse of time after used once has caused the applying tip to dry up. This is because the valve in the applicator not being used is closed to seal up the ink in the reservoir not to flow towards the tip. Even if the valve is opened again, the ink effluent from the reservoir will advance forwards merely at a limited and considerably low rate, failing to dissolve the dried ink and thus making it impossible to use the applicator any longer.
Therefore, a third object of the invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip and improved such that even a long-term non-use might not dry up the said tip.
In the prior art writing tools, the spring has a sufficient biasing force so as to urge the valve body to firmly close the opening in the valve chamber, regardless of structure and/or size of the valve opening and the valve body. It is a matter of course that even such as strong biasing force is weaker than a writing pressure, because the valve body should be retracted a small distance when the tools are used. If the spring has an excessively high ‘spring constant’ (or more adequately ‘spring modulus’), then actual biasing forces would vary among the springs undesirably due to slightly poor precision in dimension of molded members or in works for assembling them, impairing the performance of the writing tools. It is experimentally known that the writing pressure is usually 120 gf (viz., ‘gram·force’) or so in the conventional marking pen type of the writing tools. Accordingly, the biasing force is to be about 100 gf or less for the springs, and springs having a ‘spring constant’ of about 0.01 kg/mm have been employed for the purpose of quality assurance. In this case, the biasing force of finished products may be included in a range of 100±10 gf even if a dimensional error of about 0.1 mm were found in relevant members or parts. A maximum permissible value of the spring constant has been about 0.04 kg/mm.
As discussed just above, spring constant of the springs urging the spherical valve bodies or balls in the prior art has been designed as small as possible. However, as will be seen in FIG. 1(b) in the Gazette 9-323495, the ball tends to collide with a rear stopper in the valve chamber, with a bump or clunk. This motion of the ball will give to the user's hand an unpleasant feeling, when he or she uses the writing tool.
Therefore, a fourth object of the present invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip when the tip is retracted a little by the writing pressure to open the valve, and of the following design. This applicator has to be improved such that a biasing member urging the valve towards its closed position has a biasing force that is balanced with the writing pressure only at an instant when the valve is opened. This structure will eliminate the feeling of collision, allowing the user to make a pleasant writing.
In addition to the drawbacks discussed above and inherent in the prior art applicators, there is another problem resulting from a structure that any ink pool is not formed outside the ink delivery opening in the valve. If the applying tip faces up for a long time while the applicator is used upside down, the valve kept open due to the writing pressure will allow an amount of ambient air to enter the valve chamber, from fore to aft. As a result, the ink and the back-flow inhibitor disposed behind same will tend to move back and to consequently flow out through the proximal opening of the ink reservoir, due to gravitational force.
Therefore, a fifth object of the present invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip by means of a ink feed valve opened slightly when the applicator is used, and improved such that the ink is prevented from flowing back even when writing is done ‘downside up’.
It is still another problem that bubbles entrained in the ink reservoir of the prior art applicator will allow the back-flow inhibitor to slide in a reverse direction towards the proximal end, particularly when the distal end of the applicator is kept up.
Therefore, a sixth object of the present invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip, with a back-flow inhibitor being disposed behind a column of the liquid for application. This applicator has to be improved herein such that the liquid is prevented from dripping down to impair the smooth and continuous writing property. In this applicator, the back-flow inhibitor has to be retained in position not to slip off the reservoir so that leakage of the liquid is prevented from flowing out from the reservoir proximal end.
Further, each of the prior art applicators has to be constructed such that the applying tip is held in place to be capable of being retracted a limited distance, with this tip's rear end being kept in contact with a ball, i.e., a valve body. However, somewhat variation in dimension of the manufactured constituent members has sometimes caused the tip rickety fore and aft. Every time when the applicator is used repeatedly, the tip's rear face will be pressed against the ball, producing a small dimple in the rear face due to plastic deformation thereof. In such an event, the tip would be become more rickety so that not only vibrations are produced in the writings, but also the writing feeling is impaired.
Therefore, a seventh object of the present invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip when the applying tip is retracted by a writing pressure to open the valve, and improved such that the tip is protected from undesirable rickety movements.
FIGS. 2 to 5 in the Gazette 9-323495 shows the prior art examples wherein the valve chamber (viz., valve housing) is substantially of a cylindrical shape with a thick peripheral wall. A valve seat and a spring rest are formed in the inner peripheral surface of said cylinder. However, such a valve chamber causes lower manufacture efficiency and a higher production cost.
It may be possible to employ a thinner cylindrical valve chamber retained in an end plug disposed in distal end of the ink reservoir. In this case, a distal end of such a valve chamber will easily be caulked at its distal outer periphery to provide a valve seat tapered towards the distal end. Mass production of those valve chambers may be feasible at a lowered cost, though the applying tip must have a proximal end having a diameter relatively larger than that of the opening formed in each of such valve chambers. This structure intended to prevent the dripping of the ink would inevitably cause a certain problem that the tip's proximal end face is forced against the constricted distal end of the valve chamber and/or against the spherical valve body of a reduced diameter. Consequently, a small dimple will be produced in said end face before long also in this case whereby the tip is rendered rickety. Further, the spherical valve body will come into a loose and idle engagement with an enlarged dimple, failing to be pushed back.
Therefore, an eighth object of the present invention is to provide an applicator of the type that a liquid slowly exudes from a reservoir into an applying tip, and improved such that the tip's proximal end face is protected from deformation while affording a high efficiency in manufacture of the applicators.
It has been a further problem in the prior art applicators that the valve once opened with the writing pressure imposed to the tip sometimes tends thence to stand open, causing superfluous discharge of ink. In order to avoid this problem, a stopper may be formed in the applicator to restrict retraction of the tip. Such a stopper will however give an unpleasant bumping or clunking feeling to the user when the tip collides with the stopper. A means for biasing the valve body is necessitated in this case in addition to this body, making it difficult to lower manufacture cost below a certain limit.
Therefore, a ninth object of the present invention is to provide a novel structure for a delivery valve dispensing a liquid to be applied, wherein the valve is capable of opening in response to the writing pressure or by intentionally thrusting inwards the tip in an improved manner. In detail, this structure, that does not need any biasing means in addition to the valve body itself, has to be effective to avoid the dripping of the application liquid ink. It is further desirable and now possible to protect the users from any unpleasant bumping or clunking feeling when they begin writing.
The Utility Model Laying-Open Gazette No. 6-79586 discloses an example of the prior art applicators each having a valve assembly disposed in a distal region of the ink reservoir. Also in this type, an applying tip is movable a limited distance fore and aft, so that the tip may be retracted to push back a valve body to open the valve assembly, thereby feeding a liquid to the tip for the writing purpose. In its inoperative position, the valve stands closed to interrupt the feeding of said application liquid.
In order to prevent the tip from being retracted beyond a limit in one embodiment of this prior art, the distal end of reservoir will abut against a shoulder formed in the proximal portion of said tip, with said distal end thus serving as a stopper. In another embodiment, a valve receiver disposed in the reservoir may abut against a valve body that is being pressed back with the tip, with said retainer as an alternative stopper. In any case, collision takes place between the tip's shoulder and the valve assembly's distal face, or between the valve body and the receiver. Thus, a bumping or clunking feeling will be given the user, making him or her unpleasant.
Therefore, a tenth object of he present invention is to buffer the described collision so as to diminish such an unpleasant feeling of bumping or clunking.
The Patent Laying-Open Gazette No. 7-266782 discloses a slit valve that is opened by thrusting inwards a pen-point tip so that ink held in a reservoir is fed to this tip. The slit valve (i.e., resilient body 8) in the prior art writing tool is a cylinder having a bottom in which cutouts are formed. The distal face of the bottom inclusive of the cutouts is in a close contact with the proximal face of the pen-point tip. In this type structure, the ink pressure imparted to a bottom of the slit valve tends to open those cutouts in normal (viz., inoperative) state of each writing tool. However, the rear face of each pen-point tip will hinder the slit valve cutouts from opening, although the latter will be allowed to open by retracting the tip. This will cause the ink to flow from the reservoir to the tip so as to supply thereto said ink, thereby making the writing tool ready for use.
In this type prior art writing tool, the slit valve cutouts will open wider when the tip is pressed back deeper. Consequently, a superfluous amount of ink will flow through the valve undesirably remaining open, causing the ink to drip off the tip.
Therefore, an eleventh object of the present invention is to provide a structure simplified but effective to inhibit an ink or the like application liquid from dispensed even if the tip is pressed back excessively, so as to avoid the problem of ink dripping.
The Patent Laying-Open Gazette No. 62-78486 discloses a writing tool such as a fiber bundle pen or a correction pen as well as a cosmetic tool such as a manicure liquid applicator. Also, an applying tip may be pressed back to exude the liquid such as ink into this tip applying them to a foreign object. The applicator of this type comprises a liquid holding reservoir, an aperture formed in distal end of the reservoir and discharging the liquid, and a valve body for opening and closing the aperture. A biasing member always urges the valve body forwards to normally keep the aperture closed. The applying tip disposed ahead the reservoir has a rear end in contact with the valve body, so that the aperture will open to be supplied to and around the tip's rear end when this tip is pressed back against resilient force of the biasing member. The tip's rear portion will absorb the liquid thus fed thereto, with the liquid subsequently migrating forwards within said tip. In use, the distal or forward end of this applying tip may be put onto and dragged along a paper sheet or a nail, so as to apply the liquid thereto.
However in the described prior art applicators, an idle long elapse of time after used once has caused the applying tip to dry up. This is because the liquid feeding aperture in the applicator not being used is closed to seal up the liquid in the reservoir not to flow towards the tip's proximal region. Even if the aperture is opened again by retracting the tip, this tip will scarcely absorb the liquid effluent from the reservoir, so that an excessive amount of the liquid falls down along the tip's outer periphery, causing the dripping of said liquid.
Therefore, a twelfth object of the present invention is to provide a liquid applicator of the type that the liquid in a reservoir is fed to and around the proximal end of an applying tip in response to retraction thereof, and improved such that any long elapse of time after use does not cause dry up of said applying tip.